1st electric traffic light system installed, August 5, 1914
The system was designed by James Hoge, and patented in 1918. His "municipal traffic control system" displayed electrically-powered STOP and MOVE signs mounted on posts at each corner of an intersection that were wired to a manually-operated switch housed inside a control booth nearby.
The introduction of the traffic light allowed police officers directing traffic to move inside a glass booth on the corner where they controlled the light and reported accidents or emergencies.
The new system used visual, acoustic, telegraph, and telephone signals to connect the lights and emergency services. The signals were electrically interlocked, making conflicting signals impossible.
In the early days of cars, the roads were filled with pedestrians, bicycles, horses and streetcars. As early as 1868, a device with two semaphore arms was used to control traffic in London. However, those signals used lights at night that were powered by gas, and after a gas leak caused an explosion, they were removed.
In 1912 police officer Lester Wire created one of the first traffic signals when he installed a box similar to a wooden birdhouse with red and green lights inside and a manual switch on the pole, at the intersection of South and Main Street in Salt Lake City, UT. A replica of the light was displayed by the Utah Department of Transportation to celebrate it's 100th anniversary (photo on right).
Salt Lake City would debut the first interconnected traffic signal system capable of making remote signal timing changes in 1917.
In 1920 a four-way, three-light signal that is commonly used today was first used in Detroit, MI. Engineering advances continue to improve traffic lights which now employ sensors in the road to make signal adjustments and LEDs and light-diffusing optics for the lights.
- Karl Benz drives the first automobile, July 3, 1886
- Including security codes in battery packs, car electronic systems, and traffic signals
- Mixed-signal costume
For more moments in tech history, see this blog. EDN strives to be historically accurate with these postings. Should you see an error, please notify us.
Editor's note: This article was originally posted on August 5, 2013 and edited on August 5, 2017.